Injury-induced upregulation of bFGF and CNTF mRNAS in the rat retina.

Focal mechanical injury to the retina has been shown to slow or prevent photoreceptor degeneration near the lesion site in two animal models of retinal degeneration, inherited retinal dystrophy in the Royal College of Surgeons (RCS) and light damage in albino rats. Thus, when injured, the rat retina activates a self-protective mechanism to minimize damage. To identify injury responsive factors and cells, we examined the mRNAs for the following factors and some of their receptors: basic and acidic fibroblast growth factors (bFGF, aFGF) and FGF receptor-1 (FGFR1); ciliary neurotrophic factor (CNTF) and CNTF receptor alpha (CNTFR alpha); brain-derived neurotrophic factor (BDNF) and its receptor trkB; and insulin-like growth factor-1 (IGF-1) and IGFR-1 receptor (IGF-1R). After a single mechanical lesion to the subretinal space and retina, there was a substantial increase in bFGF and CNTF expression that persisted for the entire 10 d period of study. The increase in bFGF mRNA after injury was prompt and great in amplitude, while the elevation of CNTF mRNA was relatively slower. In addition, there was a transient increase in FGFR1 mRNA. In situ hybridizations showed that the elevation of bFGF and CNTF was localized to the vicinity of the lesion. The expression of GFAP (glial fibrillary acidic protein) mRNA also increased in response to injury. These findings strongly suggest that increases in endogenous bFGF and/or CNTF play key roles in injury-induced photoreceptor rescue.